/Engine/Source/Runtime/Core/Public/Misc/MapErrors.h
{Actor} : Brush has NULL BrushComponent property - please delete!: This warning is caused when there is a Brush with a "None" ConstraintInstance component. It is usually found in older maps where duplication was used to create a Brush and can be fixed by deleting the Brush causing the warning and creating a new one.
static [FLazyName](API\Runtime\Core\UObject\FLazyName) BrushComponentNull;